OpenGear CM4116 Review

I recently started paying more attention to the OpenGear CM4116 remote console server that was installed at my work before I arrived. Ever since I arrived, I thought of it as more of a pain than a useful tool. This was mostly because it was configured to provide only serial console access to servers and storage devices through an SSH tunnel.

I don’t like serial connections. I think I’m a generation too young to have a love affair with RS232 serial communication. First of all, I like the ability to open more than one shell at a time. Yes, there are tools such as GNU screen to multiplex a single terminal into many but I’m a simple guy, I prefer many graphical SSH terminals to a single multiplexed serial terminal.

Recently, I decided I would look more closely into this device after I had it shut down for some time. I was able to discover that our installed firmware version was from 2005 and lacked many of the much more interesting (to me) features of the device including tunneling network connections to hosts and IPMI-based power device control. I promptly installed the newest firmware and was on my way to remote console bliss.

Physical

This device is physically simple:

1U Rackmount

1 10/100 Ethernet Port

1 DB-9 Serial Management Port

16 RJ-45 Serial Ports

It’s not very deep at all, about half as deep as most 24/48 port switches out there.

Functionality

With the 2005 firmware, I would have given this product a pretty low score for functionality but since OpenGear has provided so many features and benefits in the new firmware, I have to give them credit where credit is due. While the entire feature list is too long and would be pointless to repeat, I will mention the features I find most useful and interesting:

SSH tunneling to 16 independent serial ports

SSH tunneling to any number of network hosts

IPMI power control for network hosts

Any UDP or TCP port can be tunneled through SSH

Web configuration & Java applet terminal

Serial ports are RF-45 so you can use standard CAT5/e/6 for serial connections with proper DTE adapter

As you can see the main feature list, while not novel, is impressive. All tunnels are pre-configured through the web-interface and can be accessed by directly SSH-ing into the box or using the SDT Connector software to manage connections to tunnels from your client system.

I’m currently using serial tunnels for two CORAID systems that are managed over serial consoles. I also use serial consoles to most of my main servers in the event that they somehow loose network connectivity. Think of the serial consoles as my backup.

I’m not using the IPMI power control yet but I plan to setup as many IPMI-capable systems to be controlled via the CM4116 as the ultimate remote management fall-back.

Performance

Performance is the one area where I feel this product could do better. While console sessions don’t lag, I find there is too much waiting time for the initial password prompt on the device when accessing it with SSH as well as the web interface. The web interface just seems to take a bit longer than I’d like to submit changes. Not a big deal but something to consider.

As for multi-user performance, I haven’t really put it to the test yet. I will be opening it up for two other individuals to use but I know they will only use it on rare occasions. So, in this regard I can say the device performs adequately for multiple sessions at once but I cannot vouch for it under multi-user, multi-session conditions.

On a much more positive note, the device powers on and boots up quite quickly. This of course is rather unimportant unless for whatever reason you end up power cycling the device over and over again.

Conclusion

Because I wasn’t around when this device was purchased, I don’t know exactly what it cost (Update: It was just around $700!). Thus, I cannot make judgments on whether it lives up to it’s cost (it does!) but I can say it’s an excellent remote console tool to have around for small shops. For larger shops OpenGear makes larger more powerful units.